JPH01106903A - Turbine nozzle - Google Patents

Abstract

PURPOSE:To improve efficiency, by a method wherein an axes at two joint end parts of a nozzle vane are formed in a linear shape. CONSTITUTION:Axes alpha1 and alpha2 at joint end parts between an adjacent nozzle vane 1a, a diaphragm outer ring 2, and an inner ring 3 are formed in a linear shape, and are inclined in the direction of the belly part of the nozzle vane 1a based on a reference line E passing the rotation center of a turbine. An axis alpha3 at an intermediate part is curved in the direction of the belly. Working fluid coming in a position in the vicinity of the peripheral walls of the diaphragm inner and outer wheels 2 and 3 is pressed against a peripheral wall surface, and development of a boundary layer is suppressed. This constitution enables improvement of efficiency through reduction of incurring of a secondary loss.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a turbine nozzle for an axial flow turbine, and in particular to suppressing the development of a boundary layer that occurs on the peripheral wall surface of an annular flow path of the turbine nozzle. The present invention relates to a turbine nozzle that can improve turbine performance by preventing the generation of secondary flows and reducing pressure loss due to secondary vortices generated when the secondary flows are roughly disturbed.

(Prior Art) In recent years, it has become an important issue to improve turbine performance in order to improve the operational economy of power plants and improve power generation efficiency.

In order to improve turbine performance, it is necessary to reduce pressure loss in each turbine stage. Internal losses in the turbine stage include airfoil loss, leakage loss, outflow loss, etc.
Particularly in turbine stages with small aspect ratios and low nozzle blade heights, the ratio of secondary loss due to secondary flow is dominant, and reducing this airfoil loss is a major issue in improving turbine performance. ing.

FIG. 7 shows the nozzle configuration of a typical axial flow turbine. A plurality of nozzle blades 1 are fixedly installed in an annular flow path 4 formed between a diaphragm outer ring 2 and a diaphragm inner ring 3.

Further, as shown in FIG. 4, a plurality of rotor blades 5 are disposed on the downstream side opposite to the nozzle blade 1. The movable shafts m5 are arranged in rows at predetermined intervals in the circumferential direction of the outer periphery of the rotor disk 6. A shroud 7 is fixed to the outer peripheral end of the rotor W5 in order to fix the rotor blade tip and to prevent leakage of working fluid.

Next, a mechanism for generating a secondary flow in the nozzle blade 1 in the above paragraph configuration will be explained with reference to FIG. 7. FIG. 7 is a perspective view of the turbine nozzle shown in FIG. 4, viewed from the nozzle outlet side.

Each nozzle blade 1 is shown as an example in which it is not inclined with respect to a reference line F passing through the center of rotation of the rotor disk 6, but is disposed perpendicularly to the outer peripheral surface of the diaphragm inner ring 3.

When the working fluid such as high-pressure steam flows through the inter-blade flow path between adjacent nozzle blades 1.1, it is bent into an arc shape in the flow path. At this time, centrifugal force is generated from the back surface B of the nozzle blade 1 in the direction of the ventral surface F, and since this centrifugal force and static pressure are in balance, the static pressure on the ventral surface F becomes high, while the flow rate of the working fluid on the back surface B is large, so the static pressure is low. Therefore, a pressure gradient is generated in the flow path from the ventral surface F side to the back surface B side.

This pressure gradient is the same in the slow flow layer, that is, the boundary layer, formed on the peripheral wall surfaces of the diaphragm outer ring 2 and the diaphragm inner ring 3.

However, near the boundary layer, the flow velocity is low and the centrifugal force acting is also small, so the flow from the ventral surface F side to the back surface B side cannot resist the pressure gradient from the ventral surface F side to the back surface B side.
Thus, a secondary flow 8 is created.

The secondary flow 8 collides with the back surface B side of the nozzle blade 1 and rolls up, generating secondary vortices 9a and 9b at both the joint ends of the inner ring side and the outer ring side of the nozzle blade 1, respectively.

The energy possessed by the working fluid is thus partially dissipated to form the secondary vortex 9.

The secondary vortex 9a is thus generated within the nozzle flow path.

9b causes non-uniform flow of the working fluid, which significantly reduces nozzle performance, and also causes energy loss of the working fluid flowing into the downstream rotor blade 5, reducing the performance of each turbine stage.

Various turbine nozzle structures have been studied in order to reduce the secondary flow loss caused by the secondary vortices 9a and 9b generated within the nozzle flow path.

For example, Japanese Patent Laid-Open No. 53-90502 discloses a configuration of a turbine nozzle that reduces the thickness of a boundary layer that develops on the peripheral wall surface of an annular flow path. FIG. 8(a) is a sectional view showing a conventional turbine nozzle, and shows an example in which a boundary layer control rod 10 is arranged in a boundary layer generation region on the upstream side of a nozzle blade 1. This boundary layer control rod 10 is intended to reduce the thickness of the boundary layer that develops on the peripheral wall surface, thereby reducing pressure loss due to secondary flow.

FIG. 9 is a sectional view showing a conventional example of a turbine nozzle disclosed in Japanese Patent Application Laid-Open No. 52-54809, in which a suction hole 11 is provided at the joint end on the ventral surface F side of the nozzle blade 1; A blow-off hole 12 is provided at the joint end of the blow-off hole 12 to form a communication hole 13 that passes from the suction hole 11 to the blow-off hole 12 .

Adjacent nozzles 1111 .
1, the secondary flow flowing from the ventral surface F side to the back surface B side is reduced as much as possible.

Furthermore, FIG. 10 shows a turbine nozzle disclosed in Japanese Utility Model Application No. 52-148802, in which the diaphragm outer ring 2
Alternatively, this is a conventional example in which a baffle plate 14 is disposed between adjacent nozzle blades 1 on the peripheral wall surface of the diaphragm inner ring 3.

The secondary flow 8 is suppressed by the baffle plate 14 having a height exceeding the thickness of the wall boundary layer of the working fluid that is expected to occur.

(Problems to be Solved by the Invention) However, in the conventional turbine nozzle shown in FIG. This makes it possible to suppress secondary flows to some extent. However, Fig. 8 (b
), the velocity distribution G of the turbine working fluid is disturbed, causing a large velocity deficit in the mainstream working fluid on the secondary side of the boundary layer control rod 10, which can be a means to fundamentally improve turbine performance. Not yet.

Furthermore, as shown in FIG. 9, in a conventional turbine nozzle in which a communication hole 13 is provided at the base of the nozzle blade 1, in the flow path between the adjacent nozzle blades 1, from the ventral surface F side of one nozzle blade 1. , the secondary flow generated on the back surface B side of the other nozzle blade 1 can be significantly reduced. However, since the flow sucked in from the ventral surface F side is blown out to the back surface B, there is a risk that the flow line of the main flow of the working fluid will be greatly disturbed, and the pressure loss may conversely increase.

Further, according to this conventional example, the structure of the communicating hole 13 is complicated, and the machining process must be set at a high level, so that there is a problem that the machining and manufacturing cost increases.

Furthermore, in a conventional turbine nozzle in which a baffle plate 14 is provided between the nozzle blades 1 as shown in FIG. 10, the baffle plate 14 is provided on the peripheral wall surface of the annular flow path 4.
Although the flow crossing between the nozzle blades in the vicinity of the peripheral wall surface is reduced to some extent, the secondary flow 8 from the ventral surface F side of the nozzle TA1 to the baffle plate 14 or the back surface B side of the nozzle m1 installed adjacently from the baffle plate 14 Since the secondary flow 8 leading to the above remains unresolved, there is a problem that it does not directly lead to a significant reduction in the pressure loss of the secondary flow.

The present invention has been made to solve the above problems, has a simple structure, suppresses the development of a boundary layer that occurs on the peripheral wall surface of the annular flow path of a turbine nozzle, and suppresses the development of a boundary layer caused by secondary flow. An object of the present invention is to provide a turbine nozzle that can reduce pressure loss due to the generation of secondary vortices and improve turbine performance.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention arranges a plurality of nozzle blades in a row in the circumferential direction of an annular flow path formed between a diaphragm inner ring and a diaphragm outer ring. , a turbine nozzle in which each nozzle blade is fixed at a joint end on the inner ring side of the diaphragm and a joint end on the outer ring side of the diaphragm,
The axis line at the inner joint end of the nozzle blade is formed into a straight line,
and the joint end is joined so that the axis line is inclined toward the ventral surface of the nozzle W with respect to a reference line passing through the rotation center of the turbine, and the axis at the intermediate portion of the nozzle blade is formed to be curved toward the ventral surface. It is characterized by

(Operation) According to the turbine nozzle having the above configuration, the axis at the inner joint end of the nozzle blade is formed in a straight line, and the axis is directed toward the ventral surface of the nozzle blade with respect to a reference line passing through the rotation center of the turbine. Because of the slope, the working fluid that has flowed into the vicinity of the peripheral wall surface of the diaphragm inner ring is pressed against the peripheral wall surface of the diaphragm inner ring, while the working fluid that has flowed into the vicinity of the peripheral wall surface of the diaphragm outer ring is pressed against the peripheral wall surface of the diaphragm outer ring. be done. Therefore, the development of boundary layers on both wall surfaces is effectively suppressed, and furthermore, the growth of secondary vortices generated on the back side of each nozzle blade due to the secondary flow is suppressed.

In addition, since the axis of each nozzle W in the middle part is curved in the direction of the ventral surface, the streamline of the working fluid distributed parallel to the middle part in the span direction from the rejoining Bi part changes smoothly. , no major disturbance occurs. Therefore, even when the working fluid flows into the rotor blades, there is little pressure loss due to mixing between the rotor blades.

As described above, according to the present invention, the secondary loss at the inner joint end of each nozzle blade is reduced, and the mixing loss between the rotor blades is also reduced, so that the turbine efficiency can be significantly improved.

(Example) Next, an example of the present invention will be described in FIGS. 1 to 6 of the attached drawings.
This will be explained with reference to the figures. FIG. 1 is a perspective view showing the structure of a turbine nozzle according to the invention, and shows an example observed from the nozzle outlet side. Further, FIG. 2 is a cross-sectional view showing the shape of the nozzle blade 1, and the same elements as those in the conventional example shown in FIG. 7 are given the same reference numerals, and the explanation thereof will be omitted.

The turbine nozzle according to this embodiment has a diaphragm outer ring 2
and an annular flow path 4 formed between the inner ring 3 and the diaphragm inner ring 3.
A plurality of nozzles 111a are arranged in a row at predetermined intervals in the circumferential direction. The tip-side and root-side joint ends of each nozzle blade 1a are joined to a diaphragm outer ring 2 and a diaphragm inner ring 3, respectively.

As shown in FIG. 2, each nozzle blade 1a has straight axes α and α2 at both joint ends, and the axes α and α2 are relative to a reference line E passing through the rotation center of the turbine. The joining ends are joined so as to be inclined toward the ventral surface of the nozzle blade 1a by an angle θ7° θ1, respectively. Further, the axis α3 at the intermediate portion of the nozzle blade 1a is formed to smoothly connect to both axes of the inclined portion and curve toward the ventral surface.

Another nozzle! Height ρ of the inclined joint end of 1Q1a
p is nozzle! O1γ・t is set in the range of 05 to 0.35 for the total height of g11a.

Further, the inclination angle θ θ of the joint end portion is set to 2.5 to 25 degrees with respect to the reference line Eγlt. Also, nozzle 11
The cross-sectional shape of a is formed uniformly over the entire blade span direction.

In the turbine nozzle according to this embodiment, the working fluid that has flowed into the inclined portion on the side of the diaphragm outer ring 2 flows along the inclined abdominal surface F of the nozzle blade 1a and is pressed against the peripheral wall surface of the diaphragm outer ring 2. Therefore, the development of a boundary layer on the peripheral wall surface is suppressed, and the generation of secondary vortices is prevented.

On the other hand, since the working fluid that has flowed into the inclined part on the side of the diaphragm inner ring 3 is similarly pressed against the peripheral wall surface of the diaphragm outer ring 3, the development of a boundary layer on the peripheral wall surface is suppressed and pressure loss due to secondary vortices at the slope part is reduced. be done.

In addition, in the middle part of the nozzle m1a, the axis α3 is formed to have a smooth curved shape in the direction of the ventral surface, so that the streamline of the main flow of the working fluid is not greatly disturbed, and the rotor blade of the working fluid The mixing loss between 5 and 5 is also suppressed.

As a result, pressure loss throughout the nozzle g1a is reduced, and turbine efficiency can be significantly improved.

Furthermore, with reference to FIG. 3, the effect of reducing pressure loss will be explained. FIG. 3 is a graph showing the distribution of total pressure loss at the outlet of the turbine nozzle shown in FIG. 1 in comparison with the conventional example. Compared to the total pressure loss of the conventional turbine nozzle shown in FIG. 7, according to this embodiment, the pressure loss distribution in the middle region of the nozzle blade 1a is almost similar. On the other hand, the pressure loss at both the joint ends on the root side and the tip side of the nozzle blade 1a is significantly reduced compared to the conventional example.

Further, with reference to FIG. 4, changes in streamlines of the working fluid flowing through the turbine nozzle of this embodiment will be explained. FIG. 4 is a streamline diagram of the turbine stage viewed from the meridional plane. The streamlines in the conventional turbine nozzle, which are not shown by broken lines, are formed substantially parallel, and no deviation in the radial direction is observed.

On the other hand, the streamlines in the turbine nozzle of this embodiment shown by solid lines are slightly offset in the radial direction near the diaphragm outer ring 2 and the diaphragm inner ring 3. This deviation is due to the fact that both joining ends of the nozzle R11a are configured to be inclined, so that the working fluid is pressed against the respective peripheral wall surfaces. This pressing force suppresses the development of a boundary layer on the peripheral wall surface and prevents the generation of secondary vortices.

In addition, the streamline of the working fluid passing through the middle part of the nozzle blade 1a has a nozzle! Since the axis of the intermediate part of IJ1a is smoothly curved, no large disturbance occurs and the result is almost similar to that of the conventional example. Therefore, there is little pressure loss due to mixing of the working fluids in the flow path between the rotor blades 5 as well.

Next, the effect on the turbine stage efficiency η when the height p and the inclination angle θ of the inclined portion of the nozzle EQ1a are changed will be explained. FIG. 5 is a graph showing the relationship between the inclination angle θ of the inclined part of the nozzle blade 1a and the turbine stage efficiency η. It is found that the turbine stage efficiency ratio exceeds 1.0 within the range, and exhibits an effect superior to that of the conventional example.

Further, FIG. 6 is a graph showing the relationship between the height p of the sloped part of the nozzle 11a and the turbine stage efficiency η1 in comparison with a conventional example, and the horizontal axis shows the height of the sloped part with respect to the total height of the nozzle blade 1a. While the dimensionless value expressed as a ratio of 1 (ρ/h) is displayed, the vertical axis shows the height ρ of the slope from 0.05 to the total height of the nozzle blade 1a, as shown in FIG. 6 of the conventional example. It is demonstrated that setting the range to 0.35 improves the turbine stage efficiency η1 compared to the conventional example.

Note that, as shown in Fig. 2, the height fJ g and the inclination angle θa, θ1 and γ゛ of the inclined part of the nozzle blade 1a do not necessarily have to be the same value at both joint ends, and the flow rate of the working fluid Different values may be set in consideration of distribution characteristics and the like.

In addition, in FIG. 2, the trailing edge line 15 of each nozzle blade 1a is joined starting from the intersection of the reference line E and the inner and outer rings 2 and 3 of the diaphragm, but the reference lines differ between the inner ring side and the outer ring side. The intersection point may be used as the starting point.

As explained above, according to the turbine nozzle of this embodiment, the axes α 1 and α 2 of the nozzle blade 1a at both joint ends are formed in straight lines, and the axes α 1 ° α 2 of the nozzle blade 1a are aligned with respect to the reference line. Since the annular flow path 4 is inclined in the direction of the ventral surface F, the working fluid flowing into the vicinity of the circumferential wall surface of the annular flow path 4 is guided along the inclined ventral surface F and is pressed in the direction of the circumferential wall surface. Therefore, the development of the boundary layer on both wall surfaces is effectively suppressed,
Furthermore, the secondary flow suppresses the growth of secondary vortices 9a and 9b generated on the back side of each nozzle blade 1a, so the pressure loss of the working fluid at the turbine nozzle is reduced.

In particular, the inclination angle of the inclined part of the nozzle blade 1a is 2.5 to 25.
The height 9 of the slope is set within the range of
When the height is set within the range of 0.05 to 0.35 degrees with respect to the total height of a, the degree of improvement in turbine stage efficiency becomes remarkable.

Further, since the axis α3 at the intermediate portion of each nozzle blade 1a is smoothly curved in the direction of the ventral surface, the streamlines of the working fluid are not subjected to large disturbances. Therefore, even when the working fluid flows into the rotor blades 5, there is little pressure loss due to mixing. In other words, since pressure loss throughout the nozzle 11a is reduced, turbine efficiency can be significantly improved.

〔Effect of the invention〕

As explained above, according to the turbine nozzle according to the present invention, both joint ends of each nozzle blade are configured to be inclined toward the ventral surface of the nozzle blade, so that the working fluid flowing into the vicinity of the peripheral wall surface is , are pressed in the direction of the peripheral wall surface of the die 17 flamm on the inner and outer ring sides. Therefore, the development of a boundary layer on the peripheral wall surface is blocked, and the generation of secondary flows and secondary vortices is effectively suppressed.

In addition, because the axis of the nozzle blade in the middle part is curved toward the ventral surface, the flow line of the working fluid is less likely to be disturbed, and there is less pressure loss due to mixing of the working fluid in the flow path between the rotor blades. .

That is, the pressure loss across the nozzle blades can be significantly reduced, and thus the turbine efficiency can be significantly improved.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of a turbine nozzle according to the present invention, Fig. 2 is a sectional view showing the shape of a nozzle blade, and Fig. 3 is a conventional example of the total pressure loss distribution of the turbine nozzle of this embodiment. Fig. 4 is a cross-sectional view showing the streamlines of the working fluid entering the turbine nozzle of this embodiment compared to the conventional example, and Fig. 5 shows the inclination angle of the nozzle blade and the turbine stage efficiency ratio. 6 is a graph showing the relationship between the height of the inclined part of the nozzle blade and the turbine stage efficiency ratio, FIG. 7 is a perspective view showing the structure of a conventional turbine nozzle, and FIG. 8 (
8(a) is a cross-sectional view showing a conventional turbine nozzle equipped with a boundary layer control rod; FIG. 8(b) is a cross-sectional view showing the velocity distribution of the working fluid in the turbine nozzle shown in FIG. 8(a); This figure is a plan sectional view showing a conventional turbine nozzle in which a communication hole is provided in the nozzle blade joint, and FIG. 10 is a plan sectional view showing a conventional turbine nozzle in which a baffle plate is provided between the nozzle blades. 1.1a... Nozzle blade, 2... Diaphragm outer ring,
3... Diaphragm inner ring, 4... Annular flow path, 5...
- Moving blade, 6... Rotor disk, 7... Shroud, 8... Secondary flow, 9.9a, 9b... Secondary vortex, 1
0... Boundary layer control rod, 11... Suction hole, 12...
Blowout hole, 13... Communication hole, 14... Baffle plate, 15.
... Trailing edge line, B ... Back surface, F ... Ventral surface, G ... Velocity distribution of working fluid, E ... Reference line passing through the rotation center of the turbine, K ... Streamline, α1. α2゜α ・・・Axis line,
h...Nozzle blade total height, θ, θ θ3
γlt...
・Inclination angle, ρ, 1 p ... Inclined part height, η. γ° t η0. η1...Turbine stage efficiency. Representative Patent Attorney Nori Chika Ken Shu
First child Maru Kenki Boku◇ Mu

Claims (1)

[Claims] 1. A plurality of nozzle blades are arranged in a row in the circumferential direction of the annular flow path formed between the diaphragm inner ring and the diaphragm outer ring, and each nozzle blade is connected to the joint end on the diaphragm inner ring side and In a turbine nozzle configured to be fixed at the joint end on the outer ring side of the diaphragm, the axes at both joint ends of the nozzle blade are formed in a straight line, and the axis line is aligned with the reference line passing through the rotation center of the turbine. A turbine nozzle characterized in that the joint ends are joined so as to be inclined in the direction of the ventral surface, and the axis of the nozzle blade at the middle part is curved in the direction of the ventral surface. 2. The turbine nozzle according to claim 1, wherein the axes of the nozzle blades at both joints have an inclination angle of 2.5 to 25 degrees with respect to the reference line.